Pituitary monoamines of the cat with special reference to the presence of an unidentified monoamine-like substance in the adenohypophysis.

Abstract

In the pituitary gland of the cat, dopamine (M.V. 0.78 μg/g), noradrenaline (M.V. 0.29 μg/g) and 5-HT (M.V. 0.94 μg/g) have been found. With the histochemical fluorescence method, a rich system of delicate fluorescent varicose fibres, often provided with irregular swellings or droplets, was observed in the neural lobe and pars intermedia. Microspectrofluorimetrically, these fibre structures exhibit the spectral characteristics of catecholamines. Most cells in the pars intermedia and a large number of cells in pars distalis show a yellowish fluorescence, with microspectrofluorimetric characteristics which differ entirely from those of the catecholamines and 5-HT. In animals treated with reserpine, the pituitary dopamine, noradrenaline, and 5-HT are largely depleted. However, the intensity and the spectral properties of the cellular fluorescence are not affected by this treatment, whereas the fluorescent fibres can no longer be seen. Thus none — or only little — of the catecholamines and 5-HT but some other monoamine-like substance is stored in the fluorescent cells of the adenohypophysis. Preliminary studies suggest that this substance is closely related to or perhaps identical with tryptamine.